1.1 SYK-inhibitors
The present invention describes new substituted naphthyridines that inhibit the protein kinase Syk (spleen tyrosine kinase), the preparation and formulation thereof and their use for preparing a medicament.
Syk is an intracellular tyrosine kinase that has an important mediator function in the signal transduction of different receptors in B-cells, mast cells, monocytes, macrophages, neutrophils, T-cells, dendritic cells and epithelial cells. The receptors in which Syk performs an important function in signal transduction include for example the receptors for IgE (FcεRI) and IgG (FcγR1) on mast cells and B cells, the B-cell receptor (BCR) and the T-cell receptor (TCR) on B- and T-cells, the ICAM1 receptor (ICAM1R) on epithelial cells of the respiratory tract, the DAP12-receptor on natural killer cells, dendritic cells and osteoclasts, the dectin 1-receptor on a subpopulation of T-helper cells (Th-17 cells), as well as the integrin receptors for β1-, β2- and β3-integrins on neutrophils, monocytes and macrophages (Wong et al.; Expert Opin. Investig. Drugs (2004) 13(7), 743-762; Ulanova et al.; Expert Opion. Ther. Target (2005) 9(5); 901-921; Wang et al.; J. Immunol. (2006) 177, 6859-6870; LeibundGut-Landmann et al.; Nature Immunology (2007) 8, 630-638; Slack et al., European J. Immunol. (2007) 37, 1600-1612). The best description is of the molecular processes during the signal transduction of the FcεRI. In mast cells the binding of IgE to FcεRI causes the cross-linking of IgE-receptors and the recruiting and activation of Lyn (a tyrosine kinase from the Src family). Active Lyn phoshorylates so-called ITAM motifs, which are present in may of the receptors listed above, and thereby generates binding sites for the SH2-domain of Syk. As a result of the binding to the ITAM motif Syk is activated and then phosphorylates various substrates which are needed for the release of allergic and inflammatory mediators such as e.g. histamine and β-hexosamidase (βHA), as well as for the synthesis of lipid mediators, such as e.g. prostaglandins and leukotrienes.
In view of its central function in different signal transduction pathways Syk has been discussed as a therapeutic target for different diseases such as e.g. Allergic rhinitis, asthma, autoimmune diseases, rheumatoid arthritis, osteopenia, osteoporosis, COPD and various leukaemias and lymphomas (Wong et al.; Expert Opin. Investig. Drugs (2004) 13(7), 743-762; Ulanova et al.; Expert Opion. Ther. Target (2005) 9(5); 901-921; Sigh and Masuda. Annual Reports in Medicinal Chemistry (2007) Vol 42; 379-391; Bajpai et al.; Expert Opin. Investig. Drugs (2008) Vol 15 (5); 641-659; Masuda and Schmitz; PPT (2008) Vol 21; 461-467).
Allergic rhinitis and asthma are diseases associated with allergic reactions and inflammatory processes and involving different cell types such as e.g. Mast cells, eosinophils, T-cells and dendritic cells. After exposure to allergens has occurred, the high affinity immunoglobulin receptors for IgE (FcεRI) and IgG (FcγR1) are activated and induce the release of pro-inflammatory mediators and bronchoconstrictors. An inhibitor of the Syk kinase activity should thus be able to inhibit these steps.
Rheumatoid arthritis (RA) is an autoimmune disease in which the bones and ligaments structures surrounding the joints are progressively destroyed. In the pathophysiology of RA, B-cells play a significant role, as has been demonstrated for example by the therapeutic use of rituximab, a B cell-depleting antibody. In addition to the function of Syk in the signal transduction of the BCR (which after being stimulated also induces the release of pro-inflammatory mediators), Syk also plays an important part in the maturation and proliferation of B cells (Cheng et al. Nature (1995) 378, 303-306, Cornall et al., PNAS (2000) 97(4), 1713-1718). An inhibitor of the Syk kinase activity might thus offer a therapeutic option for the treatment of autoimmune diseases such as RA and diseases with an increased proliferation of B cells, such as e.g. B-cell lymphocytes.
Chronic obstructive pulmonary disease (COPD) is characterised by a successive deterioration in lung function and chronic inflammation of the airways, which is initiated and produced by noxious substances of all kinds and contributes to the maintenance of the course of the disease. At a cellular level, in COPD there is in particular a multiplication of T-lymphocytes, neutrophils, granulocytes and macrophages. In particular, there is an increase in the number of CD8-positive lymphocytes, that is directly connected with the impairment of lung function. Another characteristic of COPD are acute deteriorations in lung function (exacerbations), characterised by viral (e.g. Rhinovirus), or bacterial (e.g. Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis) infections.
In view of the pro-inflammatory function of Syk in macrophages, T-cells and neutrophils as described above (see: Wong et al.; Expert Opin. Investig. Drugs (2004) 13(7), 743-762; and references cited therein) an inhibitor of the Syk kinase activity could be a new therapeutic approach to the treatment of the inflammatory processes that underlie COPD. It has also been shown that Syk in epithelial cells of the respiratory tract is involved in the ICAM1R-mediated uptake and subsequent replication of the Rhinovirus and that a si-RNA against Syk blocks these steps (Wang et al.; J. Immunol. (2006) 177, 6859-6870; Lau et al.; J. Immunol. (2008) 180, 870-880). Thus, an inhibitor of the Syk kinase activity could also be used therapeutically in exacerbations caused by Rhinoviruses.
Various studies suggest that Syk is involved in the malignant transformation of lymphocytes (summarised in Sigh and Masuda. Annual Reports in Medicinal Chemistry (2007) Vol 42; 379-391). A TEL-Syk fusion protein with a constitutive Syk activity transformed B cells of a patient with myelodysplastic syndrome, a constitutively active ITK-Syk fusion protein was isolated from patients with T-cell lymphomas. Moreover, constitutively active Syk was found in B-cell lymphoma cells of patients. On the basis of these data it seems that Syk is a proto-oncogene in haematopoietic cells and represents a potential target for the treatment of certain leukaemias and lymphomas.
1.2 Prior art
BE 835770 describes 5-amino-1,6-naphthyridine with an antimicrobial activity. U.S. Pat. Nos. 3,928,367, 4,017,500, 4,115,395 and 4,260,759 describe 5-amino-1,6-naphthyridines with an antifungal and antibacterial activity. WO 9918077 describes 5-piperazinyl-1,6-naphthyridines as serotonin antagonists. U.S. Pat. No. 7,321,041 describes substituted [1,6]-naphthyridines as SYK-inhibitors, although they have a completely different substitution pattern from the compounds according to the invention.